A variety of techniques are currently available for in vitro delivery of nucleic acids to cells and organelles, such as, transfection, microinjection, and electroporation. However, most of these techniques are not suitable for delivering nucleic acids or genes in vivo.
Receptor-mediated gene transfer is often used for introducing nucleic acids into suitable recipient cells, both in vitro and in vivo. This procedure involves attachment of nucleic acids to a ligand through a polycationic protein (usually poly-L-lysine), wherein the ligand is selected to target a specific receptor on the cell surface. Upon incubation with the recipient cells, the nucleic acids are delivered to the recipient cells through a receptor-mediated uptake mechanism. However, the expression level of the introduced transgene is dependent on several highly variable factors, such as, the stability of the nucleic acid-ligand complex, the presence and number of specific receptors on the recipient cell surface, or the receptor-ligand interaction.
As such, there is a need for a nucleic acid delivery vehicle that is stable enough to transfer sufficient amount of nucleic acids to the cells and a need for a consistent and reliable method for facilitating delivery of the vehicle. Although there exists a potential method that could be used for nucleic acid delivery to the cell, which is known as ‘biolistic’ nucleic acid delivery, this method does not reproducibly suited for existing protocols for preparing nucleic acid coated particles. The biolistic method is based on mechanical delivery of nucleic acid-coated particles into the cells or organelles using high-pressure-air propelled. Biolistic nucleic acid delivery is typically used for stable or transient transformation of nucleic acids to cells, and this delivery method is more suitable for delivery of plasmids and large nucleic acid fragments. Currently used nucleic acid-coated particles for biolistic delivery suffers from three disadvantages: 1) the amount of nucleic acids associated to each particle is less, and previous attempts to increase nucleic acids to each particle resulted aggregation of the particles; and 2) the loss of nucleic acids from the particles while the particles traverse through multiple layers of cells, and 3) the inability of the delivered nucleic acid to be localized into a cell, or into the nucleus of a cell. Thus, developing better nucleic acid-coated particles via more robust and reliable protocols is highly desirable.